Rotors which must have magnetic characteristics are used in electric motors. For this, for permanent magnet motors, it is known to embed permanent magnets into a rotor. Moreover, it is known from EP 17 199 16 A1 to design the rotor in a shaftless manner and completely of magnetic material, wherein then the individual magnets of the rotor are formed by way of a suitable magnetization of the magnetic material in the rotor.
The rotor must be mounted in the electric motor in the axial and radial direction. Thereby, as the case may be, it is not only the forces produced by the rotor itself, but also the external forces which are transmitted from elements connected to the rotor onto the rotor, which need to be accommodated by the bearings. For example, it may be the case in a pump assembly that the axial forces caused by the impeller and also the radial forces acting on the impeller must be transmitted directly onto the rotor of the electric motor and be accommodated by its mounting.
With a rotor which is formed completely of magnetic material, under certain circumstances it is difficult to design the bearings in a sufficiently strong manner, in order to be able to accommodate the occurring forces. For this reason, it is known from EP 17 199 16 A1 to embed additional bearing sleeves into the magnetic material. This however entails increased manufacturing and assembly costs.